The invention relates to the field of infrared (IR) inspection of turbine components, such as turbine blades, turbine vanes, and other turbine items of the like having internal passages for cooling or other liquid/gas flow. More specifically, the invention relates to automated analysis of the thermal response of a turbine component to application of thermal stimuli to the turbine component by an IR inspection system to inspect the turbine component.
Failure of a turbine component, such as a blade or a vane is costly, and may even be catastrophic. Accordingly, manufacturing a turbine component involves precision casting and machining processes, as each of these processes may introduce variables that affect the quality of the component, and in turn, its performance and reliability.
During the casting process, variables such as core misalignment, inclusions, and the like, can introduce casting defects into the components. Often times, these casting defects in turn may affect the machining process, resulting in machining defects, as well.
For example, a turbine component may include features such as cooling channels and holes. Cooling channels are internal features of the component through which coolants (e.g. in the form of gases) may flow. Because of the internal nature of the cooling channels, cooling channels are, often times, formed during the casting process utilizing casting cores. Defects, such as core misalignments may result in incorrectly formed, sized or blocked cooling channels.
The cooling holes allow the coolant flowing through the component to be exhausted out of the component. The dimension of the cooling holes may be in the range of 10ths of millimeters. Because of the small dimension of the cooling holes, often times, the cooling holes are machined into the component after the casting process. In order to control the precision of machining the cooling holes, an automated process may be utilized for the physical drilling of the holes, such as computerized numerically controlled (CNC) machine.
Drilling the cooling holes by CNC machine involves the CNC machine determining the exact position of the cooling holes in three-dimensional space, accounting for dimensional tolerances. If casting defects, such as core misalignments, affect the dimensions of the component to the extent that the dimensional tolerances are exceeded, the cooling holes may not be drilled properly.
Recently, inspection methods involving thermal signatures of materials, in particular, infrared (IR) detection imaging, are being utilized to inspect and detect defects in the manufacturing of turbine components. A turbine component inspection method utilizing IR imaging involves applying differential thermal stimuli to the turbine components. Often times, applying differential thermal stimuli involves delivering a first thermal stimulus, such as a gas, at a high temperature to the component, and then, following the high temperature thermal stimulus, delivering a second thermal stimulus, such as a gas, at a cold temperature (i.e., cold, relative to the high temperature thermal stimulus) to the turbine component. An example of an IR inspection apparatus may be found in co-pending U.S. Provisional Pat. Application No. 60/339,765 titled TURBINE COMPONENT INSPECTION SYSTEM, filed on Nov. 1, 2001, and having at least partial common inventorship with the present application. The application is incorporated herein in its entirety by reference.
To ensure the high precision turbine components are inspected properly, the inspection itself, including e.g. the application of the thermal stimulus, is preferably performed with great precision each time, with the inspection system properly calibrated. Moreover, minimal to virtually no judgment should be required of the operators, to avoid human error. Prior known systems all suffer from varying degrees of not able to ensure consistent application of thermal stimuli to inspections of different turbine components or different inspections of the same turbine component. Moreover, too often, too much operator judgment is required in determining whether a turbine component passed or failed an inspection. Thus, a computer assisted method, including automated analysis of the turbine components"" thermal response to the applied thermal stimuli, and automated pass/fail conclusion, is desired.
In accordance with a first aspect of the present invention, thermal response of a turbine component to application of thermal stimuli to the thermal component is automatically analyzed by regions of interest.
In accordance with another aspect, each region is analyzed for conformance for a number of thermal response metrics. In various embodiments, the conformance is analyzed in an absolute sense, as well as relative to a reference/primary region.
In one embodiment, the thermal response metrics include the temperature threshold a particular region (e.g. the reference/primary region) exhibits a critical response size, and that the sub-region achieving the critical response size at the temperature threshold also has a critical shape.
In one embodiment, the analyses are performed using the pixel values of the constituting pixels of a picture frame of the turbine component""s thermal response.
In accordance with yet another aspect, a binary passed or failed conclusion is reached based on the results of the automated analyses.
In one embodiment, a computing apparatus is equipped with executable instructions designed to perform the automated analyses.